Advanced video signal processing systems such as high definition television (HDTV) systems typically use digital signal processing. As part of such digital signal processing, data is typically rearranged in a prescribed sequence prior to transmission, followed by restoration to the original sequence upon reception. This operation serves to spread or disperse the data in time in a predetermined sequence, such that a data loss during transmission does not result in a loss of contiguous data. Instead, any data lost is dispersed and is therefore more easily concealed or corrected. Apparatus used to rearrange the original data sequence prior to transmission is commonly referred to as an interleaver, and apparatus used to restore the original data sequence upon reception is referred to as a deinterleaver. The interleaving/deinterleaving process is well known. Scrambling, in contrast to interleaving, has as its main goal the randomizing of data and the dispersal of transmitter signal energy. This helps to minimize co-channel interference and enhance timing recovery in the receiver. Scrambling also facilitates channel distortion compensation by an equalizer in the receiver.
Different interleaving/deinterleaving algorithms are known. For example, European satellite systems currently employ an algorithm proposed by Forney as described in "Burst-Correcting Codes for the Classic Bursty Channel," IEEE Transactions on Communications Technology, vol. COM-19, October 1971. A different algorithm proposed by Ramsey as described in "Realization of Optimum Interleavers," IEEE Transactions on Information Theory, vol. IT-15, May 1970, is commonly used in the United States.